The first retail worker strike against Walmart has spread from Los Angeles, where it began last week, to stores in a dozen cities, a union official said Tuesday.

Walmart workers walked off the job in Dallas, Seattle, the San Francisco Bay area, Miami, the Washington, D.C., area, Los Angeles, Sacramento, Chicago and Orlando, said Dan Schlademan, director of the United Food and Commercial Workers’ Making Change At Walmart campaign. Workers also went on strike in parts of Kentucky, Missouri and Minnesota, he said.

Tuesday’s walkouts included 88 workers from 28 stores — a minuscule fraction of the 1.4 million who work at Walmart, the world’s largest private employer. Until Friday, when about 60 Walmart employees walked off the job for a day in LA, no Walmart retail workers had ever gone on strike, the union said.

The workers are protesting company attempts to “silence and retaliate against workers for speaking out for improvements on the job,” according to a United Food and Commercial Workers news release. Walmart workers, who are not unionized, have long complained of low pay and a lack of benefits.

Some striking Walmart associates plan to protest Wednesday at a Walmart annual investor meeting at its headquarters in Bentonville, Ark., said a striking worker.

“I make $8.90 an hour and I’ve worked at Walmart for three years,” said Colby Harris, 22, of Dallas. “Everyone at my store lives from check to check and borrows money from each other just to make it through the week.” The six heirs to Walmart founder Sam Walton, meanwhile, are worth $89.5 billion, oras much as the bottom 41.5 percent of Americans combined.

David Tovar, the retailer’s vice president of communications, said the unhappy strikers “aren’t representative of our entire associate base.”

“We do surveys and our associate satisfaction scores have been improving over the past couple years, which runs counter to what a few workers who show up at events that the unions put them up to would say,” said Tovar. He said Walmart’s employee turnover rate is lower than the retail industry average.

Harris, who works in the produce department in Lancaster, Texas, belongs to OUR Walmart, the UFCW-backed worker organization that planned Tuesday’s strike in Dallas and the others across the country. Harris said it’s not just the wages that bother him. Walmart harasses and fires workers who join labor groups or complain about company policies, he said. “But I’d rather lose my job than be treated like this.”

Tovar said Walmart has a policy of listening to complaints from workers. “We have an open-door policy,” he said. “If you have any kind of issue you should bring it forward to your manager and if it isn’t resolved to your satisfaction you can go to the next level of management.”

Walmart also disputed the UFCW’s claim that the strikes this week were the first ever. “The UFCW has done these same publicity stunts in the past,” said Tovar, citing a 2006 walkout at a Walmart store in Hialeah Gardens, Fla.

However, the walkout in Hialeah Gardens was not exactly an organized union strike. In that case, workers with no ties to union groups spontaneously walked out of a store after an abrupt scheduling change, according to reports from the Miami Herald and Bloomberg news. Tuesday’s strikes, meanwhile, had been planned for weeks.

“They say [these strikes] are an attempt to get attention,” said Harris. “But if we were getting the attention we deserved, we wouldn’t be protesting.” He added: “I’m not being paid for these days. We’re taking off work to protest — obviously there must be something wrong.”

Non-union workers employed in Illinois and California warehouses owned by Walmart also went on strike earlier this month.